The present invention relates to a motorcycle particularly of a scooter-type structure.
With respect to a motorcycle particularly having a scooter-type structure in which a portion between a handle bar and a driver""s seat is considerably curved downward into a U-shape to form a straddling foot space extending in a transverse direction of a motorcycle (vehicle) body and low-floor type footrest floors, on which feet of a driver are to be rested, are formed on the opposite sides of the bottom portion of the straddling foot space, there exists such a scooter- type motorcycle as described, for example, in Japanese Patent Laid-Open Publication No. HEI 11-129969, in which an engine provided with a cylinder assembly disposed substantially horizontally is mounted in the vicinity of the footrest floors, an intake device is disposed along a down-tube, which extends rearward downward from the lower portion of the head pipe and an intake pipe directly connects the above-mentioned intake device with the engine.
In the scooter-type motorcycle described in the above-mentioned publication, the engine is utilized as a reinforcing member (i.e., a diamond-framework structure) for a body frame and the body frame is provided at the rear portion with a pivot member by which a swing arm is swingably supported.
Alternatively, there exists a scooter-type motorcycle as described, for example, in Japanese Patent Laid-Open Publication No. HEI 11-105764, in which a body frame is divided into two parts in the longitudinal direction of a motorcycle body, between which an engine is mounted so as to provide a reinforcing member, and the engine is provided at the rear portion with a pivot member by which a swing arm is swingably supported.
When an engine capable of performing a high output at a low rotational speed as in the scooter-type motorcycle is demanded, an intake passage is increased to thereby improve an intake efficiency of the engine by utilizing an intake pulsation, making the engine output characteristic to a low velocity type output characteristic.
In a case where the intake device is disposed along the down-tube extending from the lower portion of the head pipe and the intake pipe directly connects the above-mentioned intake device with the engine, a distance between the head pipe and the engine is, however, too small to provide a necessary length for the intake passage.
In a case where the engine is utilized as a part of the body frame or the engine supports the swing arm, it is necessary to increase the strength of the engine, leading to an increased weight thereof.
In a case where a drive pulley for a V-belt type automatic transmission device is secured to the end of a crankshaft of the engine and such a V-belt type automatic transmission device is placed so as to deviate from the engine as in the scooter-type motorcycle as described in the above-mentioned Japanese Patent Laid-Open Publication No. HEI 11-129969, the width of the engine in the transverse direction thereof increases, and application of the cradle-type framework structure, in which the body frame encloses the engine, causes the width of the body frame to increase further larger than that of the engine, thus exerting an influence on a bank angle.
An object of the present invention, which was made taking into consideration the above-described circumstances, is to substantially eliminate defects or inconveniences encountered in the prior art mentioned above and to provide a motorcycle, particularly of a scooter-type, provided with an intake passage having an increased length thereof.
Another object of the present invention is to provide a scooter-type motorcycle, which restrains a width of a body frame from increasing even when the cradle-type framework structure is applied.
These and other objects can be achieved according to the present invention by providing, in one aspect, a motorcycle in which a body frame and a body cover, located between a head pipe for steerably supporting a front wheel in a bilateral direction through a front fork and a driver""s seat, are curved downward into a U-shape to form a straddling foot space extending in a transverse direction of a motorcycle body; low-floor-shape footrest floors, on which feet of the driver are to be rested, are formed on opposite sides of a bottom portion of the straddling foot space and a central portion between the footrest floors is formed into a shape of tunnel; and an engine unit, which has a crankcase including a V-belt type automatic transmission device provided with a drive shaft disposed so as to be separated from and in parallel to a crankshaft extending in the transverse direction of the motorcycle body and with a driven shaft, and which has a cylinder assembly disposed substantially horizontally in a front portion of the crankcase, is placed in the tunnel shaped portion,
wherein an intake device is received in a rising portion of the tunnel shaped portion, the intake device being provided with a cleaner box including an air cleaner, with a throttle body disposed on a downstream side of the cleaner box and with a surge tank disposed on a downstream side of the throttle body; the throttle body and the surge tank are placed side by side above the cylinder assembly of the engine unit, and the cleaner box is placed above the throttle body and the surge tank; and the respective elements are connected by means of pipes so as to provide an S-shape structure in a plan view.
In a preferred example of this aspect, a radiator for cooling the engine unit is disposed on a front side of the cylinder assembly, the radiator being provided with a cooling fan for cooling the cooling water received in the radiator and the cooling fan being placed on a side of the surge tank in the transverse direction of the motorcycle body in a rear side of the radiator.
Moreover, leg shields are formed on opposite sides of the rising portion of the tunnel shaped portion and pocket spaces are formed in upper spaces of the leg shields on opposite sides of the cleaner box, respectively.
In another aspect of the present invention, there is also provided a motorcycle in which a body frame and a body cover, located between a head pipe for steerably supporting a front wheel in a bilateral direction through a front fork and a driver""s seat, are curved downward into a U-shape to form a straddling foot space extending in a transverse direction of a motorcycle body; low-floor-shape footrest floors, on which feet of the driver are to be rested, are formed on opposite sides of a bottom portion of the straddling foot space and a central portion between the footrest floors is formed into a shape of tunnel; and an engine unit, which has a crankcase including a V-belt type automatic transmission device provided with a drive shaft disposed so as to be separated from and in parallel to a crankshaft extending in the transverse direction of the motorcycle body and with a driven shaft, and which has a cylinder assembly disposed substantially horizontally in a front portion of the crankcase, is placed in the tunnel shaped portion,
wherein a power transmission direction change device for changing a rotational direction of the driven shaft to transmit a driving power of the engine unit to a propeller shaft for power transmission to a rear wheel is provided on a side of the engine unit; a pair of lower down-tubes extend rearward downward from a lower portion of the head pipe, pass through a space between the crankshaft and the power transmission direction change device and then extend rearward upward; a pair of main tubes extend rearward along an upper surface of the engine unit from rising portions of the lower down-tubes, to connect to the lower down-tubes at a rear side of the engine unit to form a loop-shaped frame in a side view; a sub-frame is detachably provided on a lower side of a connection portion of the main tubes and the lower down-tubes; and the sub-frame supports a suspension device for the rear wheel and a link mechanism for shock absorbers for supporting the suspension device.
In this aspect, the sub-frame supports the engine unit and a main stand of the motorcycle body.
In a further aspect of the present invention, there is also provided a motorcycle in which a body frame and a body cover, located between a head pipe for steerably supporting a front wheel in a bilateral direction through a front fork and a driver""s seat, are curved downward into a U-shape to form a straddling foot space extending in a transverse direction of a motorcycle body; low-floor-shape footrest floors, on which feet of the driver are to be rested, are formed on opposite sides of a bottom portion of the straddling foot space and a central portion between the footrest floors is formed into a shape of tunnel; and an engine unit, which has a crankcase including a V-belt type automatic transmission device provided with a drive shaft disposed so as to be separated from and in parallel to a crankshaft extending in the transverse direction of the motorcycle body and with a driven shaft, and which has a cylinder assembly disposed substantially horizontally in a front portion of the crankcase, is placed in the tunnel shaped portion,
wherein a primary drive gear for transmitting rotation of the crankshaft to the drive shaft is provided at one end of the crankshaft, the V-belt type automatic transmission device is disposed on an opposite side, the crankcase expands downward at a lower portion thereof on a side of the primary drive gear to form an oil pan in the crankcase, and an exhaust pipe, which has a base portion connected to a lower portion of the cylinder assembly, passes through a space below the V-belt type automatic transmission device in a vicinity of a side member of the oil pan to extend rearward.
According to the subject structures and characteristic features of the present invention, an intake device is received in a rising portion of the tunnel shaped portion, the intake device being provided with a cleaner box including an air cleaner, with a throttle body disposed on a downstream side of the cleaner box and with a surge tank disposed on a downstream side of the throttle body; the throttle body and the surge tank are placed side by side above the cylinder assembly of the engine unit, and the cleaner box is placed above the throttle body and the surge tank; and the respective elements are connected by means of pipes so as to provide an S-shape structure in a plan view. It is therefore possible to ensure an intake passage having a long scale, achieving a low velocity type output characteristic of the engine.
According to the feature that a radiator for cooling the engine unit is disposed on a front side of the cylinder assembly, the radiator being provided with a cooling fan for forcedly cooling the cooling water received in the radiator and the cooling fan being placed on a side of the surge tank in the transverse direction of the body in a rear side of the radiator, it is possible to improve cooling efficiency of the radiator.
According to the feature that leg shields are formed on opposite sides of the rising portion of the tunnel shaped portion and the pocket spaces are formed in upper spaces of the leg shields on opposite sides of the cleaner box, respectively, it is possible to use effectively a useless dead space in a conventional structure.
Furthermore, according to the present invention, the power transmission direction change device for changing a rotational direction of the driven shaft to transmit a driving power of the engine unit to a propeller shaft for power transmission to a rear wheel is provided on a side of the engine unit; a pair of lower down-tubes extend rearward downward from a lower portion of the head pipe, pass through a space between the crankshaft and the power transmission direction change device and then extend rearward upward; a pair of main tubes extend rearward along an upper surface of the engine unit from rising portions of the lower down-tubes, to connect to the lower down-tubes at a rear side of the engine unit to form a loop-shaped frame in a side view; a sub-frame is detachably provided on a lower side of a connection portion of the main tubes and the lower down-tubes; and the sub-frame supports a suspension device for the rear wheel and a link mechanism for shock absorbers for supporting the suspension device. Therefore, it is possible to reduce the distance between the lower down-tubes in the transverse direction of the vehicle body and improve the assembling and maintenance properties of the motorcycle.
According to the feature that the sub-frame supports the engine unit and the main stand, it is possible to improve assembling and maintenance properties thereof.
According further to the present invention as described above, the primary drive gear for transmitting rotation of the crankshaft to the drive shaft is provided at one end of the crankshaft, and the V-belt type automatic transmission device is disposed on an opposite side; the crankcase expands downward at a lower portion thereof on a side of the primary drive gear to form an oil pan in the crank case; and an exhaust pipe, which has a base portion connected to a lower portion of the cylinder assembly, passes through a space below the V-belt type automatic transmission device in a vicinity of a side member of the oil pan to extend rearward. It is therefore possible to ensure a sufficient bank angle and a sufficient ground clearance, and it is also possible to prevent the temperature of oil received in the oil pan from increasing.
The nature and further characteristic features of the present invention will be made more clear from the following descriptions with reference to the accompanying drawings.